How to play Worstfish
- Choose to play White, Black or a random side, then make your move by clicking or dragging a piece.
- Worstfish looks at every legal move with the Stockfish chess engine and plays the one that scores worst for itself, such as hanging its queen or walking into mate.
- Try to checkmate it in as few moves as you can: the page counts your moves and keeps your fastest checkmate. Or take the harder challenge and get Worstfish to checkmate you: those are counted too, with your fastest.
- Pick Worstfish vs Worstfish to watch it play itself, from the start or from where your game is. Press Space or Pause to stop it and move for either side, and pick White or Black to take a side back. The Eval bar beside the board shows who a strong engine thinks is winning; untick it to hide it.
Things to try against Worstfish
- Go for a speed run. Checkmate it in as few moves as you can. Worstfish blunders its king’s safety right away.
- Win with pawns only, without moving your queen, rooks, bishops or knights.
- Lose on purpose. Try to get Worstfish to checkmate you. It will avoid mating you as hard as it can, so this is the real challenge.
- Avoid captures. See how long you can go without taking any of the pieces it throws at you.
How it works
Worstfish runs the Stockfish 10 chess engine in your browser, the same one used on the chess page. On its turn, it asks the engine to look a few moves ahead and score every legal move, then picks the move with the lowest score for itself. Ties are broken at random, so games don’t repeat. Everything happens on your device.